The present invention relates to a process for preparing compounds of the molecular structure represented by the formula: ##STR3## wherein X is selected from the group consisting of:
(A) WHERE THE COMPOUNDS ARE TETRAHYDROPYRAN TYPE COMPOUNDS ##STR4##
(b) where the compounds are 1,4-dioxane type compounds: ##STR5## and
(C) WHERE THE COMPOUNDS ARE TETRAHYDROFURAN TYPE COMPOUNDS: ##STR6## and wherein R is selected from the group consisting of alkali metal, ammonium, trialkanolammonium, and lower alkyl, branched or straight chain, with up to about C.sub.20 in the chain, comprising:
(A) PREPARING A SUITABLE HALO DICARBOXY ESTER OF AN ALDEHYDE OF THE GENERAL FORMULA ##STR7## wherein M is halogen, X is as defined above, and R' is lower alkyl, preferably ethyl or methyl.
(B) CYCLIZING THE COMPOUND OF (A) TO THE CYCLIC CYANO DIESTER INTERMEDIATE OF THE FORMULA: ##STR8## wherein X and R' are as given above, and
(c) hydrolyzing the intermediates to Step (b) to the corresponding salts, and if desired, converting the salts to the corresponding triesters or acids.
The salt compounds produced in accordance with the process of the present invention have utility as water softeners, detergent builders, calcium and magnesium sequestrants, scale dissolvers, and the like. The compounds may be used alone or as additives to a variety of solid or liquid detergent formulations. In such formulations the compounds enhance the cleaning capacity of the detergent by providing a builder, threshold or other effect. The esters are useful in synthesizing the pure salt forms of the compounds. The cyclic cyano diester intermediates are useful in preparing the end product tri-salts, esters or acids.